Power Quality

There are several reasons for the degradation of power quality. This brief explanation is intended to provide an insight into the common causes for degradation of power quality.

Harmonics:Any periodical non-sine wave can be represented as a sum of sinusoidal waves having each a frequency that corresponds to an entire multiple of the fundamental. In the mains voltage in New Zealand, the fundamental has a frequency of 50Hz, the second harmonic has a frquency of 100Hz, the third harmonic has a frequency of 150Hz, and so on. Harmonic distortion is a constant problem in industrial electrical installations and should not be confused with short events such as voltage sags, surges and fluctuations.

Causes of Harmonics:Any apparatus that alters the sinewave or uses only a part of such a wave causes distortions to the sine wave and therefore harmonics. Virtually all current signals are in some way distorted. The most common harmonic distortion is from non-linear loads such as personal computers, printers, photcopy machines, fluorescent lights, microwave ovens, or speed control devices for electric motors. This harmonic distortion causes significant currents at frequencies that are odd multiples if the fundamental frequency.

Consequences of Harmonics:Almost any component in a power system can suffer from harmonics. Machines can overheat and may even vibrate in extreme conditions. Delicate electronic equipment might malfunction of fail. Even induction motors and transformers can fail because of harmonics. The odd multiples of the third harmonic (called "Triplens") add together in the neutral of an installation and can cause overheating in neutral busbars and connecting lugs. Insulation can be overstressed, and circuit breakers can trip when there is no apparent circuit overload. Telecommunications systems can be interfered with by picking up triplen currents in the neutral. The 5th and the 11th harmonic make the operation of electric motors harder and shorten their average life, and 5th harmonics tend to disturb power factor capacitors, shortening their life and affecting their performance.

Voltage Anomalies:Voltage anomalies occur in the form of voltage sags, surges, and fluctuations beyond set thresholds above and below the nominal reference voltage (Vref of 230V RMS). Watts Projections can record and report on such occurrences of voltage anomalies.